I've been re-reading Numenera recently, preparing myself to run it at an upcoming convention. While looking through the book, I found myself really thinking about one specific mechanic: effort.
For those of you who aren't familiar with Numenera, I'll elaborate. Each character possesses three stats (Speed, Intellect, & Might) with a pool of points associated with it. Players can choose to apply effort when making a stat check, expending a point from the appropriate pool to reduce the difficulty of the check.
I really like this mechanic. Its relatively simple and represents the growing fatigue of a character rather well. I'd love to see more games utilize similar mechanics. With that in mind, I thought I'd create a version of this rule for 5th Edition. Since requiring players to lower ability scores is not very feasible, I've created two different versions.
Like the Numenera version, this application lowers the DC of the ability check. However, the player expends their character's hit points to do so. Since hit points also represent a character's stamina, I think its works as a resource pool for this. Unfortunately, I haven't decided on the actual cost for apply effort yet. My gut wants me to make the cost 2 for -2 DC, but I might keep that in flux until I discover a nice balance. The second, and easier to implement, application allows the player applying effort to receive advantage on the ability check. However, they will receive disadvantage on the next ability check to represent lingering fatigue.
While I prefer the hit point expenditure of the first application, I like the simplicity of the second one a little more. Maybe I can combine the two, allowing players to spend 2 hit points to receive advantage on the check (cutting out the additional math). I might give all three versions a test run at the table, see which one I prefer. Feel free to do the same and leave constructive criticism in the comments below.